ES2550328T3 - Filled with resin-coated radios and system and method to prepare them - Google Patents

Abstract

A deformable coated radius filler comprising a continuous or elongated fibrous structure and a sticky resin surface coating, wherein said coated radius filler has an inner portion that is substantially free of resin and the resin surface coating has a substantially uniform thickness.

Description

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DESCRIPTION

Filled with resin-coated radios and system and method to prepare them

Background

The current method for manufacturing composite materials that have complex shapes is to form a preform of reinforcing fibers in a particular way, place the preform in a vacuum bag or mold, infuse the preform with liquid resin, and then heat the impregnated preform to cure it. to the final composite piece. During the preparation of some preforms, it is usual to find an empty space or cavity in various joints formed between different depositions of fiber layers. Fillers have been conventionally used to fill such a cavity.

In US Pat. 5,026,595, fillings of woven fabric recesses having a triangular shape are described, which can be used to fill triangular shaped holes.

Radius fillers formed from braided and sticky covers are described by applying a solution thereon in US 2003/0183 067 A1.

Reinforcements of composite materials are described which include gaps reinforced by fillers wrapped with a structural adhesive in international patent application WO 2009/140 555 A2.

From U.S. Pat. 5,650,229, fiber fillers are known that are used to fill gaps between associated fiber layers.

In European patent application EP 1 094 042 A1, a method for impregnating a strand of non-twisted fiber with a polymer is described, wherein the strand of fiber is stretched through an open impregnation vessel.

A process for coating filaments with a resin is described in US 3,574,665 A, where a single filament is stretched through a resin bottle with a container of liquid mercury in the lower open hole of the bottle.

In JP Sho 64-016 612, a process for coating a bundle of continuous fibers with a molten resin is described, wherein the fiber bundle is expanded before passing through the resin melt to ensure a uniform coating and bubble free.

Compendium

The present description refers to fillings of radios useful in aerospace applications such as aircraft structural components. The radius filling is a deformable coated structure, comprising a continuous or elongated fibrous structure and a sticky resin surface coating, formed by pulling a continuous or elongated, dry fibrous structure, through a heated resin bath, in where the coated radius filler has an inner portion that is substantially free of resin, and the resin surface coating has a substantially uniform thickness.

Brief description of the drawings

FIG. 1 illustrates an illustrative braid structure that can be used to form a coated radius fill.

FIG. 2 schematically illustrates a surface coating method and system for forming a coated radius filler according to one embodiment.

FIG. 3 shows an embodiment of a buttonhole design to be used in the coating method depicted in FIG. one.

FIG. 4 is a photomicrograph of a cross-sectional portion of a coated fiber braid formed according to the coating method depicted in FIG. one.

FIG. 5 schematically shows the cross section of a type of preform structure that has a cavity to be filled with radius fillings.

FIG. 6 is a photomicrograph showing the cross section of an infused stringer structure in which two types of coated fiber braids are used as radius fillings.

Detailed description

For pieces of composite materials made of pre-impregnated materials, the usual practice has been to use the same material used in the joint section, and roll it up to form a filling. This strategy is time-consuming, inefficient and has the particular disadvantage of manufacturing fillings of limited length. To alleviate this

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inconveniently, some solutions involve manufactured preimpregnated fillers made of continuous filaments, where several filaments are impregnated either individually or clustered together. In some cases, these filaments can be passed through a nozzle to preform the filling to a desired cross-sectional profile, which mimics the profile of the cavity they will fill. One or more fillings per cavity are used, depending on the size of the cavity, the size and shape of the filling, the ability of the filling (s) to fill the cavity, the desired mechanical performance of the part and some other restrictions , such as the handling of the filling (s), the placement in the cavity, the management of the inventory of the material, etc. In another strategy, a machine is provided to take several preimpregnated tapes and produce a filling of a continuous length, and preformed to a desired profile. Such preimpregnated radius fillers have in common a large amount of resin, typically 30% to 40% by weight of the product. The distribution of the resin is such that it has generally soaked the vast majority of the fibers that form the filling. Preimpregnated fillers usually have some level of stickiness, which can be increased during the deposition process by heating the filling with a heat gun for example. The handling, flexibility and malleability of the preimpregnated fillers is usually poor, it is made difficult by the resin, which prevents the free movement of the fibrous structure of the filler, even when the filler is heated with a heat gun. Finally, in the case of composite parts made of preimpregnated materials, adhesive resin fillers were also developed as an alternative to preimpregnated fillers. In this case, the filling is made of 90% to 100% resin, occasionally with a light cloth embedded in the resin filling to provide superior handling characteristics.

In recent years, the number of composite pieces manufactured by a Resin Infusion (RI) procedure has increased considerably. RI is not only used to make small complex parts, but is also used now to make whole wings, or other very large parts of the aircraft. Although, in some cases, the formation of the pieces by a preformation procedure with fabrics can eliminate the need for a filling -in the case of preforms π for example -the vast majority of RI pieces, especially large pieces, are still based in wide genera endowed with stickiness or fabrics that are folded to form the desired shape, which creates cavities that need to be filled with fillings. Wide genres endowed with stickiness can be rolled up to a noodle-shaped filling. This method can only produce short-length fillings, and it is by far the least profitable strategy. Other strategies are based on partially impregnating individual or multiple filaments or ropes or braids with a tackifying agent. The purpose of the tackifying agent is to provide some level of tackiness to the filling, in order to position it in the cavity while the preform is being assembled. Unfortunately, most tackifiers must be heat activated to provide their tack characteristic. This requires heating the filling with a heat gun, for example, during deposition. In some cases, the tackifying agent may be a solvent-based, sprayable resin, which requires the total removal of the solvent, thus presenting safety and content problems of laminated voids. This can sometimes be a difficult task, which requires more than one operator, and can even be questionable from the point of view of the risk to safety and possible degradation of materials. Attempts to use preimpregnated fillers or solid fillers in a cavity of a part to be processed by RI have not been very successful, since the integration between the RI part and the prepreg filled, due to differences in curing cycles, does not exist , and the compatibility between the materials is poor, resulting in mechanical problems.

Finally, it has been found that preformed fillers are difficult to handle and position within the cavity to be infused with resin. The cavities of the structural pieces can have complex profiles, therefore, it is important to match the shape of the preformed filling with the profile of the cavity. This agreement requirement implies an unnecessary burden for manufacturing operators. In some applications, the profile of the cavity changes even with the location in the piece. It is therefore extremely difficult to manufacture a filling with a variant cross section that adapts to the profile of the cavity. In addition, the associated cost of such filling would be far from the need and performance of its function. In addition, many conventional pre-formed fillings are very rigid and cannot be bent, running the risk of damaging their profile, and as such, they can only be made of a discrete length for reasons of handling and shipping, limiting their attractiveness. For fillings that are somewhat less rigid, and can be rolled over very large diameter cores, e.g., 50.8 centimeters (20 inches) and more, special grooved cores are necessary to maintain the shape of the filling and prevent its twisting In addition, the amount of filler deposited in this type of core is usually limited by the spacing of the grooves and the size of the core (diameter and length). These packaging requirements increase the overall cost of such a product and reduce its attractiveness.

This description refers to coated fillers for use in composite preforms that are subjected to a resin infusion process (IR). More specifically, the coated fillings take the form of continuous or elongated fillings to fill a cavity of a three-dimensional composite material preform structure. Coated fillings are deformable and malleable so that they can conform to various cavity geometries. In one embodiment, the continuous or elongated padding to be coated is in the form of a braided, continuous, dry structure, for example, a fiber braid made of a plurality of individual fiber strands entwined in a braided pattern. FIG. 1 illustrates an illustrative braid structure that can be used to form the coated padding. The fiber braid can have a solid inner portion or a hollow core. Coated fillers are referred to herein as "radius fillers." It is also described in the

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A method of forming a surface coating of resin on a dry, continuous or elongated filler, whereby the resulting coated filler retains a sticky outer surface at room temperature, is present herein. The coated padding becomes stiffer than the original uncoated padding, but is still foldable / malleable.

The term "sticky" or "stickiness", as used herein, refers to the ability of coated fillers to stick to a surface for a period of time.

Resin Infusion (RI) is a generic term that encompasses processing techniques such as resin transfer molding, liquid resin infusion, vacuum assisted resin transfer molding, flexible stamping resin infusion, vacuum assisted resin infusion , resin film infusion, resin infusion with controlled atmospheric pressure, vacuum assisted process and single line injection. The resin infusion can be used in the manufacturing process of a structural part, in which liquid resin is stretched in a dry fibrous preform that is kept under vacuum. The dry fibrous preform may take the form of a plurality of layers or layers of dry reinforcing fibers assembled in a stack or arrangement. Then, the preform is placed in a mold or vacuum bag, and injected or infused directly in situ with the matrix resin. The filled radius fillers of the present description can be used to fill cavities formed within the dry fibrous preform.

In one embodiment, the fillings to be coated are made of uniquely designed braids that confer an adaptable deformability to fit various cavity profiles. In particular, the deformability of the padding is due to the high ratio of axial fibers to inclined fibers that form the wrap of the braid. The braids can be made of 3 or more interwoven threads, described as inclined threads that form a flexible and highly deformable hollow tube. In some cases, the axial threads are also intertwined with the inclined threads to form a flexible hollow tube with a higher cohesion, that is, the braid is more stable or less deformable. This type of braid structure is called a "triaxial" braid because the threads (that is, fiber strands) are going in three different directions, contrary to the so-called "biaxial" braid because the threads are arranged in two different directions only. In other cases, the hollow section of the braid, biaxial or triaxial, can be filled with longitudinal threads. The longitudinal threads are defined as the core of the braid, while the biaxial or triaxial structure of the braid is defined as the outer layer or sheath or sheath. When braids are used, the percentage by weight of axial fibers as fibers located in the core of the braid or / and within the inclined fibers is at least 50%, preferably above 65%, based on the total weight of the braid. The resin coating is uniformly deposited on the outer structure of the braid, leaving the inner portion of the braid substantially free of resin. This in turn allows the braid core to be infused during the RI cycle. The resin remains on and within the outer surface of the braid created by the inclined threads, due to a combination of a light layer structure and a low flow resin at room temperature.

Specific braid architectures are a function of the purpose of filling the braid and the size of the radius filling. In general, thicker braids, those with a diameter above 0.38 centimeters (0.155 inches) are used to fill the maximum volume of the cavity, and are designed with a core wrapped by a biaxial sheath, while used Thinner braids in the vertices of the cavity and have a triaxial design. However, other braid designs can be developed for other applications. In the case of the core and shell construction for the thicker braids, the core and the biaxial wrap are independent of each other and allow free independent movement in relation to each other. In addition, the core contains the vast majority of the fibers, at least 50%, of the filling, and is made of independent parallel threads that allow free movement without much restriction. This favors a good packing of the filling in the cavity. The outer shell is independent of the core with its fibers at a long angle in relation to the longitudinal direction of the braid, eg, less than 35 °. This further favors the proper handling of the filling of spokes. The outer layer has a good coverage factor, which helps to contain the resin on the braid inside the filling sheath or its surface.

In the case of triaxial braid filling, high deformability of the filling is desired to fill the vertices of the cavity. As such, the braid structure is preferably collapsible. As such, a hollow braid structure is very suitable for this purpose. The axial threads, which represent approximately 50% by weight of the braid filler, will provide good longitudinal stability, which is particularly needed during the resin coating process, and consistency in the deformability and collapsibility of the product. Similar to the core-sheath braid, the coverage of the triaxial braid is high, to help contain the resin inside the outer sheath or on its surface.

FIG. 2 schematically illustrates a method and system of surface coating to form the fillings of coated radii according to one embodiment. The method and surface coating system includes passing a continuous, dry, fibrous structure 2, eg, a fiber braid, supplied from a coil 1 source, through a bath 3 (ie, stretching longitudinally under tension) of resin heated and out through a deformable eyelet 4, whereby only the desired amount of resin is deposited on the outer surface of the filling. The coated fibrous structure leaving the heated resin bath 3 is then rolled up with an interleaving material supplied by a coil 6 before being rolled onto a storage coil 7. The interleaving material is removable and is an aid for winding and storage, and does not become a part

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integral of the finished coated padding. The interleaving material allows the coated filler to be wound on itself and unwound.

The resin coating of the radius filling is controlled by the viscosity of the resin, the coating process and the characteristics of the uncoated fibrous structure. For a given radius filling, the desired deposited amount of resin is controlled by processing conditions such as the temperature of the resin, which affects the viscosity of the resin, the line speed, which affects the residence time of the filling. coated in the resin, and the diameter of the eyelet through which the resin bath fill comes out, which affects how much resin is squeezed out of the coated fill. The inner diameter of the hole in the eyelet is controlled and works with other control factors to provide the desired coating resin content. The main control factors include:

(to)

Buttonhole opening dimension (ID dimension)

(b)

Resin temperature (which affects the viscosity of the resin during coating)

(C)

Resin level in the resin bath

(d)

Resin Age

(and)

Line speed

The contact time of the continuous filling with the resin bath is determined by the resin level and the line speed. The viscosity of the resin bath during the coating process is controlled by heating to allow a relatively smooth and uniform surface coating, and may be in the range of 0.05 Pa-s -100 Pa · s (0.50 Poises -1,000 Poises) depending on the surface of the filling to be coated (eg roughness, texture of the braid fabric). The temperature of the resin bath heated during the surface coating may be in the range of 37.78 ° C -148.89 ° C (100 ° F -300 ° F), depending on the type of resin used. Any conventional heating means can be used to heat the resin bath, for example, band heaters around a metal container to provide the heat source. Line speed may vary from 5.08 cm / s to 76.25 cm / s (10 to 150 feet per minute (fpm)), preferably 15.25 cm / s to 30.5 cm / s (30 fpm to 60 fpm ). The level of resin within the coating bath directly affects the resin content of the coated filler by increasing the residence time of the uncoated filler in the resin, therefore, it can be varied to achieve the desired resin content for the coated filler. The surface tension of the resin also acts to lower the resin level before entering the buttonhole.

The eyelet is made from a deformable material, and is sized to be the same or slightly smaller than the solid diameter of the continuous padding / braid to be coated. For example, an eyelet of 3.175 mm (0.125 inches) of ID can be used to coat a braid with 3.76 mm (0.148 inches) of outer diameter (OD), and a eyelet of 2.03 mm (0) can be used , 08 inches) of ID to cover a braid with 2.03 mm (0.08 inches) of OD. In some embodiments, to increase the resin content of the coated fill, the inner diameter of the eyelet can be increased to be slightly larger than the diameter of the continuous fill / braid to be coated. It has been found that the rubber eyelets are suitable for the coating system of the present description. It should be understood, however, that another elastomeric material can be used to make the buttonhole. FIG. 3 shows an embodiment of a suitable buttonhole design (cross-sectional view to the left, and viewed from above to the right). It should be noted that the geometry of the buttonhole can be varied to suit the different cross-sectional geometries of the filling (eg, triangle, square, oval, etc.).

The resulting coated filler produced by the coating method depicted in FIG. 2 is a deformable / malleable radius filler with a controlled resin content. The thickness of the resin coating of the coated filler is substantially uniform. The continuity of the surface coating is approximately 90% -100%. There is some penetration of the resin in the outer portion of the fibrous structure, but the inner portion of the fibrous structure remains substantially free of resin.

FIG. 4 is a photomicrograph of a cross-section of a coated fiber braid formed according to the coating method represented by FIG. 2. This cross-sectional view shows that the resin forms a coating on the outer portion of the coated braid, while the core fibers in the inner portion of the coated braid remain free of resin.

The amount of resin deposited on the uncoated filler may range from 5% to 50%, preferably 10% 30%, more preferably about 15% -20% by weight based on the total weight of the coated filler, and is adapted to meet the requirements of the intended application. The resin content and surface coating substantially prevent the coated filler from restricting the flow of resin during the RI process when the structural part is manufactured. The developed coating method described herein is very robust and stable, and allows consistent deposition of a desired amount of resin on the filler.

Fillers of resin-coated radii can be economically produced in a range of diameters of about 0.254 mm to 38.1 mm (0.010 inches to 1.5 inches) for most purposes, and can

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be in the range of 1.02 mm to 10.16 mm (0.04 inches to 0.4 inches) for certain intended purposes.

The continuous or elongated fibrous structure to be coated may be made of organic or inorganic fibers, including fibers made of polymer, carbon, graphite, glass, quartz, aramid (eg, Kevlar), PBO, polyethylene, inorganic oxide, carbide , ceramic, metal or combinations thereof.

The coating resin may be a coating formulation containing one or more thermosetting resins that include, but are not limited to, members of the group consisting of epoxy resin, addition-polymerization resin, bis-maleimide resin, ester resin of cyanate, phenolic resin, polyester resins, vinyl ester resins, and combinations thereof.

In addition, the resin may be a hot melt resin, which means that the resin is a solvent-free resin that is liquid at temperatures greater than room temperature and a solid or semi-solid at room temperature. Hot melt coating procedures are based on controlling the viscosity of the resinous polymer with temperature. When a hot melt epoxy resin is used, the resin can be preheated in an oven (eg, at 37.78 ° C -121.11 ° C or 100 ° F -250 ° F) before the start of the coating process, to allow the resin to be poured into the process vessel.

Examples of epoxy-based resins suitable for coating formulation include Cycom® 890 RTM resin and Cycom® 823 RTM resin, from Cytec industries Inc. (both are liquid epoxy resins designed for resin transfer molding). Other possible epoxy-based resins that can be used include an epoxy resin selected from N, N, N ', N'-tetraglycidyldiaminodiphenylmethane (eg "MY 9663", "MY 720" or "MY 721", marketed by Ciba -Geigy), viscosity 10-20 Pa · s at 50 ºC (MY 721 is a version of MY 720 of lower viscosity and is designed for higher use temperatures); N, N, N ', N-tetraglycidyl-bis (4-aminophenyl) -1,4-diisopropylbenzene (eg Epon 1071, sold by Shell Chemical Co.), viscosity 1.8-2.2 Pa · s) 18 -22 Poises) at 110 ° C; N, N, N ', N'-tetraglycidyl-bis (4-amino-3,5-dimethylphenyl) -1-4-diisopropylbenzene (eg Epon 1072, sold by Shell Chemical Co.), viscosity 3-4 Pa · s (30-40 Poises) at 110 ° C; p-aminophenol triglycidyl ethers (eg "MY 0510", marketed by Ciba-Geigy), viscosity 0.55-0.85 Pa · s at 25 ° C; preferably of viscosity 8-20 Pa · s at 25 ° C; preferably this constitutes at least 25% of the epoxy components used; materials based on bisphenol A glycidyl ethers such as 2,2-bis (4,4'-dihydroxyphenyl) propane (eg "DER 661", marketed by Dow, or "Epikote 828", marketed by Shell), and novolac resins preferably of viscosity 8-20 Pa · s at 25 ° C; glycidyl ethers of phenol novolac resins (eg "DEN 431" or "DEN 438", marketed by Dow); 1,2 diglycidyl phthalate, eg GLYCEL A-100; diglycidyl derivative of dihydroxydiphenylmethane (Bisphenol F) (eg "PY 306", marketed by Ciba Geigy) which is in the low viscosity class. Other epoxy resin precursors include cycloaliphatics such as 3 ', 4'-epoxycyclohexyl-3, -4-epoxycyclohexane carboxylate (eg "CY 179", marketed by Ciba Geigy) and those of the "Bakelite" range of Union Carbide Corporation.

Examples of addition-polymerization resins are acrylics, vinyls, bis-maleimides, and unsaturated polyesters.

Suitable bismaleimide resins are heat curable resins that contain the maleimide group as reactive functionality. The term maleimide, as used herein, includes mono-, bis-, tris-, tetrakis-, and higher functional maleimides and mixtures thereof as well, unless otherwise indicated. Bismaleimide resins with an average functionality of approximately two are preferred. The bismaleimide resins thus defined are prepared by the reaction of maleic anhydride or a substituted maleic anhydride such as methylmaleic anhydride with an aromatic or aliphatic di- or polyamine. The closely related nadicimide resins, prepared analogously from a di-o polyamine but wherein the maleic anhydride is replaced by a Diels-Alder reaction product of maleic anhydride or a maleic anhydride substituted with a diene such as cyclopentadiene, They are also useful. As used herein, the term "bismaleimide" will include nadicimide resins. Also useful are "eutectic" bismaleimide resin mixtures containing several bismaleimides. Such mixtures generally have melting points that are considerably lower than individual bismaleimides.

In one embodiment, the resin used for surface coating is an epoxy-based resin that has been modified with a viscosity modifier, such that the compatibility of the process and performance is preserved, but the ambient viscosity is such that it produces a tack. surface for positioning purposes and low fluidity behavior. The viscosity modifier can be selected from thermoplastic polymers and rubbers. Such modified resin is a version of the modified low fluidity resin used in resin infusion processes, which is usually a low viscosity, high fluidity resin, which satisfies the requirements of the RI process. The low fluidity resin formulation is achieved by adding a thermoplastic polymer or high viscosity rubber to the low viscosity base epoxy resin in an amount ranging from 5% to 20% based on the total weight of the resin formulation, preferably 10 at 15%, depending on the type of epoxy, the type of curing agent and the desired fluidity of the resin. In addition, the resin surface coating is formulated to be compatible with the resin infusion process with respect to tackiness and rheological behavior during the manufacture of composite structures.

The thermoplastic viscosity modifier may be selected from, but not limited to, a group consisting of cellulose, polyester, polyamide, polyimide, polycarbonate, polyurethane, poly (methyl methacrylate) derivatives,

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polystyrene, polyaromatic; Polyesteramide, polyamidaimide, polyetherimide, polyamramide, polyarylate, polyacrylate, poly (ester) carbonate, poly (methyl methacrylate / butyl acrylate), polysulfone, polyethersulfone, co-polymer of polyether ether sulfone, polyether ether ketone ether ketone ether ketone ether ketone ether ketone (polyether ketone ketone) PEKK, nylon, rubber and combinations thereof. As an example, a commercially available thermoplastic viscosity modifier that can be used is Cytec KM® 180 (polyether sulfone co-polymer (PES) and polyether ether sulfone (PEES) available from Cytec Industries).

As an example, the low fluid resin coating formulation may be comprised of an epoxy-based liquid resin, eg Cycom® 890 RTM or Cycom® 823 RTM, which has been modified by adding a PES-PEES copolymer, e.g. eg Cytec KM® 180, as a viscosity modifier.

The surface coating resin formulation may further comprise conventional additives, such as a curing agent and / or a catalyst. Additional fluidity modifiers, such as silica particles (eg Cabosil, from Cabot Corp.) can also be added to the resin coating formulation to further refine the viscosity of the resin. It should be understood that the viscosity of the resin influences the coating process, the sticking time to the outside of the coated filler, and the reaction of the filler to the RI process. "Outside tack time" refers to the exposure time to the environmental conditions during which the product can provide a tack of positioning, measured in hours or days.

The coated radius filler produced by the coating method described herein can be used to fill the radial cavity created in structural pieces of composite materials. This concept can also be used in other applications where cavities created by joining layers of fabric form a specific section that must be filled. In addition, the coated radius filler is for use in applications where composite parts are manufactured by an RI procedure.

An example of the application for coated radius fillings will be described with reference to FIG. 5. When two "L" shaped sections of fiber preforms are joined to form a "T" shaped section on a substantially flat surface, a cavity with vertices is formed. Each of the sections of the "L" shaped preform is composed of a plurality of fibrous layers. FIG. 5 shows the cross section of this type of preform structure. This type of preform structure is suitable for the manufacture of an aircraft stringer. This cavity can be filled with the filled radius fillings of the present description, and the sections of the preform together with the cavity are subsequently infused with liquid vacuum resin. Radius fillings must be easily positioned within the cavity, conform to it, and must not affect the Resin Infusion procedure or the performance of the final structural piece. The design of the filling of spokes depends on the shape and size of the cavity, as well as the position and the role of the filling in the cavity. For the application shown in FIG. 5, the cavity fillings can be based on two different braided structures, each having a specific filling paper. The first braid can have a core / sheath structure and is the thickest of the two types of braid. Its purpose is to fill the maximum space of the cavity. The second braid can have a hollow design, and its purpose is to fill the vertices of the cavity, and as such it must be highly deformable and collapsible. The braid design contributes to the good handling performance of the cavity fill. FIG. 6 is a photomicrograph showing the cross section of an infused stringer structure in which two types of fiber braids discussed above are used. The braids with the hollow design are placed in the vertices of the cavity.

The characteristics of the radio fillings manufactured in the manner described above include:

(to)

Only superficially coating the surface of the filling, a dry internal portion is retained in the coated filling that aids in the evacuation of air during the deposition process or maintaining highly permeable vacuum channels within the composite material preform.

(b)

Retaining a dry inner portion, the coated radius filling also allows a higher level of handling than one achieved with a fully impregnated filling, since the resin limits the flexibility and handling of the filling.

(C)

By modifying the resin for tackiness and handling, the coated filler product can be easily positioned (and repositioned), while optimizing life outside the filler.

(d)

Fillers of resin-coated spokes are compatible with their surroundings during resin infusion, that is, the surrounding materials.

(and)

 The addition of a thermoplastic modifier, such as Cytec KM 180, provides a degree of hardening to the base resin.

(F)

The addition of a thermoplastic modifier also modifies the stickiness to the exterior characteristic of the filling preventing the migration of the resin to the inner portion of the filling.

Coated spoke fills designed and manufactured according to the present description are affordable, and reduce

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Additionally, the overall manufacturing cost of the composite part, by simplifying the manufacturing process of the part. The resin coating process for manufacturing such a product is simple, elegant but robust, as well as very effective, and results in a final product with very little variation.

Examples

The coating method and the coated filler of the present description can be illustrated by the following non-limiting examples.

Example 1

Using the coating system illustrated by FIG. 2, a continuous dry carbon braid was coated by pulling the braid through a resin bath containing hot melt epoxy resin (Cycom® 890 RTM) 10 modified with a thermoplastic viscosity modifier (Cytec KM® 180) and out through a rubber eyelet provided at the bottom of the resin bath vessel. The braid had a biaxial envelope that surrounded a core of longitudinal axial fibers, and an outer diameter (OD) of 3.76 mm (0.148 inches). The eyelet had an inside diameter (ID) of 3.18 mm (0.125 inches). The resin bath temperature was 78 ° C (173 ° F), the resin level was 25.4 mm (1 inch), and the line speed was 24.38 cm / s (48 fpm). The resulting coated braid had

15 a resin content of 6.2% based on the total weight of the coated braid, and the inner portion of the braid was resin free.

Example 2

Using the coating system illustrated by FIG. 2, a continuous dry carbon braid was coated by pulling the braid through a resin bath containing the same resin formulation described in Example 1. The

The braid had a biaxial envelope that surrounded a core of longitudinal axial fibers, and an outer diameter (OD) of 2.03 mm (0.08 inches). The eyelet used in the resin bath vessel had an inside diameter (ID) of 2.03 mm (0.08 inches). The resin bath temperature was 51.67 ° C (125 ° F), the resin level was 50.8 mm (2 inches), and the line speed was 7.62 cm / s (15 fpm). The resulting coated braid had a resin content of 29% based on the total weight of the coated braid, and the inner portion of the braid was resin free.

Claims (18)

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one.

A deformable coated radius filler comprising a continuous or elongated fibrous structure and a sticky resin surface coating, wherein said coated radius filler has an inner portion that is substantially free of resin and the resin surface coating has a substantially uniform thickness.

2.

 The deformable coated radius filler according to claim 1, wherein the mass fraction of the resin in the coated radius filler is in the range of 10% to 30% based on the total mass of the coated radius filler.

3.

The deformable coated radius pad according to claim 1 or 2, wherein the fibrous structure is a fibrous braided structure composed of a plurality of interwoven fiber strands in a braid pattern.

Four.

The deformable coated radius filler according to claim 3, wherein the fibrous structure is a biaxial or triaxial braid.

5.

The deformable coated radius filling according to claim 3, wherein the fibrous braided structure comprises a longitudinal axial thread core and a biaxial or triaxial outer sheath.

6.

The deformable coated radius filling according to claim 3, wherein the fibrous braided structure comprises longitudinal axial threads that constitute at least 50% of the mass of the fibrous braided structure.

7.

The deformable coated radius filling according to claim 3, wherein the fibrous braided structure comprises a biaxial or triaxial outer sheath and a hollow core.

8.

The deformable coated radius filler of any one of claims 1 to 7, wherein the resin surface coating comprises an epoxy based resin.

9.

The deformable coated radius filler of any one of claims 1 to 7, wherein the resin surface coating comprises an epoxy-based resin and a viscosity modifier that modifies the characteristic exterior stickiness of the coated radius filler preventing migration of the resin to the inner portion of the fibrous structure.

10.

The deformable coated radius filler according to claim 9, wherein the viscosity modifier is selected from a group consisting of cellulose, polyester, polyamide, polyimide, polycarbonate, polyurethane, poly (methyl methacrylate), polystyrene, polyaromatic derivatives; Polyesteramide, polyamidaimide, polyetherimide, polyamramide, polyarylate, polyacrylate, poly (ester) carbonate, poly (methyl methacrylate / butyl acrylate), polysulfone, polyethersulfone, co-polymer of polyether ether sulfone, polyether ether ketone ether ketone ether ketone ether ketone ether ketone (polyether ketone ketone) PEKK, nylon, rubber, and combinations thereof.

eleven.

The deformable coated radius filler of any one of claims 1 to 10, wherein the fibrous structure comprises fibers made of polymer, carbon, graphite, glass, quartz, aramid, PSO, polyethylene, inorganic oxide, carbide, ceramic, metal or combinations thereof.

12.

 The deformable coated radius filler of any one of claims 1 to 11, wherein the outer diameter of the coated radius filler is in the range of 0.254 mm to 38.1 mm (0.01 inches to 1.5 inches).

13.

 A method of forming a resin coated radius filler, comprising:

providing a continuous fibrous structure (1) to be coated; providing a resin formulation heated in a container (3), said container (3) having a bottom wall and a deformable eyelet (4) positioned through said bottom wall, said eyelet (4) being provided with a hole a its path that is sized to allow the fibrous structure (1) to pass through and at the same time control the amount of resin deposited on the outer surface of the fibrous structure (1); and pulling the fibrous structure (1) through the resin formulation and out through the eyelet (4), whereby only a desired amount of resin is deposited on the outer surface of the filling, where the time of Contact of the fibrous structure with the resin formulation is controlled by controlling the line speed and resin level of the resin formulation in the container (3), and where the viscosity of the resin formulation is controlled to allow formation of a resin coating with substantially uniform thickness.

14.

 The method according to claim 13, wherein the fibrous structure (1) continues to be coated is in the form of a fibrous braided structure composed of a plurality of interwoven fiber strands in a braid pattern.

fifteen.

The method according to claim 13 or 14, wherein the resin formulation comprises one or more epoxy resins and a viscosity modifier to modify the characteristic exterior stickiness of the coated radius filling preventing the migration of the resin to the inner portion of the fibrous structure (1), and said modifier of

9 Viscosity is present in a mass fraction of 5% to 20% based on the total mass of the resin formulation. 16. The method according to any one of claims 13 to 15, wherein the viscosity of the heated resin formulation is maintained in the range of 50 mPa · s to 100 mPa · s (0.50 Poises -1,000 Poises), the level of resin is maintained in the range of 6.35 mm to 76.2 mm (0.25 inches -3.0 inches) inside the container, and the 5 line speed is in the range of 5.08 cm / s to 76.20 cm / s (10-150 feet per minute (fpm)). 17. A system for forming a coated radius filler, comprising: a source (2) for supplying a continuous, dry fibrous structure (1) to be coated; a resin bath heated in a container (3), wherein said container has a bottom wall and a deformable eyelet (4) positioned through said bottom wall, said eyelet (4) being provided with a hole therethrough. 10 which is sized to allow the fibrous structure to pass through and at the same time control the amount of resin deposited on the outer surface of the fibrous structure; and a mechanism (7) for pulling the continuous fibrous structure through the resin bath and out through the eyelet (4). 18. The system according to claim 17, wherein the fibrous structure (1) is in the form of a fibrous braided structure composed of a plurality of interwoven fiber strands in a braid pattern. 15 19. A three-dimensional fiber preform suitable for resin infusion, comprising: a plurality of dry reinforcing fiber layers, configured to form a three-dimensional structure with at least one cavity; and one or more fillings of deformable coated spokes according to any one of claims 1 to 12 positioned in the cavity. 10